This invention relates to spraying apparatus for cleaning horizontally displaced filter plates of a filter press.
In plate type filter presses, especially those used to dewater sewage sludge, filter cake accumulates in the chambers formed between adjacent filter plates and is discharged when the plates are pulled apart. The filter cloth on each vertical face of each filter plate tends to get clogged after a period of use, thus causing a considerable decrease in the permeability of the cloth. Accordingly, each filter cloth must be cleaned from time to time to maintain its filtering rate and performance.
With rectangular filter plates, conventional spraying apparatus is usually employed to wash the filter plates with the spray tubes of such apparatus moving either horizontally or vertically in the space between adjacent filter plates to be cleaned. Cleaning fluid under pressure is discharged from the spray tubes to clean the plates as the spray tubes move relative to the adjacent surfaces of the filter plates being cleaned. As illustrated in U.S. Pat. Nos. 3,780,747 and 4,076,033, cumbersome and complicated support frames and drive assemblies are required to move such cleaning apparatus. Such support frames are usually operatively connected to the upper supports for the filter press which in turn carries the filter plates. These support frames are adapted to travel along such supports and align the spray tubes with the space defined between adjacent filter plates to be cleaned.
So far as I am aware, such conventional filter plate washers are adapted for use only with square and rectangular filter plates. Circular filter plates are usually washed by a hand operated hose assembly having a right angle spray nozzle at its discharge end. Cleaning fluid under high pressure is discharged through the nozzle as the person handling the hose moves the spray nozzle back and forth relative to the filter plate until it is cleaned. This is a time consuming operation which must be repeated for each circular filter plate being cleaned. In the event the hose assembly should be accidentally dropped or otherwise allowed to get out of control, very dangerous and unsafe working conditions would be created due to the discharge of cleaning fluid from the hose under high pressure.
While U.S. Pat. Nos. 3,620,233 discloses a filter plate washer adapted for movement beneath the filter plates and carries a horizontal spray tube, lifting means is employed to raise and lower the horizontal spray tube in a vertical direction. With this particular arrangement, the spray tube remains horizontal at all times while moving relative to the filter plates being cleaned. To use such apparatus for washing circular filter plates would be unsatisfactory due to the fact that a substantial amount of the cleaning fluid would not strike the filter plates but would pass outside the perimeter of the filter plates. Not only would cleaning fluid be wasted, but unsafe working conditions would be created by the discharge of cleaning fluid outside the perimeter of the filter plates.
Other conventional spraying devices with which I am familiar are disclosed in U.S. Pat. No. 3,633,651 and Switzerland Pat. No. 445,455.